Bleaching fur skins



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FIPBSO CANON OF TEXTILES & FiBERS,

9 GR 1QS00Q768 Patented Dec. 26, 1933 sears BLEACHING FUR SKINS WilliamE. Popkin, Brooklyn, N. Y.

No Drawing.

Application June 12, 1930 Serial No. 460,795

8 Claims.

This invention relates to the bleaching of animal fur skins preparatoryto dyeing the same, and has for its object to provide a new and improvedmethod resulting in an improved product.

The known methods of bleaching fur skins either injure the hair fibresor discolor the skins. When fur skins are treated directly with a strongoxidizing bleaching solution, the action is so drastic that the air andleather of the skins are tendered. When the skins are first treated withmetal salts existing in two valences according to United States Patent1,573,200, prior to bleaching, there is furthermore a concomitant dyeingeffect, which leaves the hair and leather tinted with insolublecharacteristic colored compounds, the color depending on the nature ofthe metal salt used. For instance, when ferrous sulfate is used, theentire fur including hair and leather are tinted a light browncharacteristic iron oxide color. When cuprous salts are used, a greenishcolor is produced, and when manganous salts are used a purple tint isimparted to the fur skin. Furthermore, when metal salts are used theyleave the hair and leather impregnated with an undesirable deposit, asfor instance, oxidized iron, which imparts an undesirable tint to thefur, weakens the leather and hair fibres, interferes with the subsequentdyeing treatment and is generally known to result in dyed furs ofgreatly inferior quality.

It is an object of the present invention to avoid the deleterioustendering action of direct bleaching, and also to obviate the use ofmaterials which will remain as such or produce reaction products thatwill remain in or upon the fur skins after the completion of thebleaching operation, the presence of which is objectionable, and in thisway to produce bleached fur skins, which have the color, texture,strength and lustre of unbleached light fur skins.

According to my invention, the fur skins after being killed in any knownor preferred manner, as by being treated with a dilute weak alkali, {iis impregnated with what I term a cyclic oxidizing catalyst and then theimpregnated fur is img mersed in a bleaching solution, whereupon theoxygen that is liberated from the bleach is immediately taken up by thecatalyst which is contained in and adheres to the fur skin. Thebleaching effect starts promptly and its rate is controlled by thechemical liberation of oxygen from the oxidizing solution. In this way,the skins, which were originally dark colored, are bleached to a lightfiesh color unimpaired as to structural strength, lustre and texture.

The bleached skins obtained by this process may now be dyed to anylight, or other desired color in accordance with the procedures used fordyeing natural white or light colored skins.

The following is a specific example of one mode of applying the methodof the present invention; it being understood however that the followingdescription is given merely by way of illustration and that the processis not limited to the specific details of the following illustrativeexample. Brown or black Australian rabbit skins are killed in a dilutesolution of sodium carbonate. The skins are then rinsed andhydro-extracted. They are then immersed in a solution of sodiumtetraborate (borax) or an equivalent cyclic ox: i in catal t and a lowd. 9 re Overnight- While the strength of the borax solution ors'olutionof an equivalent catalyst may vary within considerable limits, I preferto use an aqueous solution of a strength of about 0.5 to about 10.0 percent sodium tetraborate. To this may be added a more or less quantity ofsalts of tartaric acid. After soaking for 8 to 12 hours the fur skinsare rinsed and the excess of borax removed. The immersion in the boraxsolution has impregnated the leather and hair of the fur skin with thecyclic oxidizing catalyst. The skins are then immersed in a solution ofnygrggenperoxr ide or equivalent oxidizifiblEzhing agent; the quantityof free oxygen in this solution being regulated by controlling thehydrogen ion concentration. The cyclic oxidizing catalyst jigging;-diately takes up"tlie"6xygn liberat''d" from the bleaching solution andforms unstable intermediate compounds which draw the bleach onto andinto the material comprising the fur skin. In this way the dark coloredskins are quickly and smoothly bleached to a light flesh color. Thebleaching operation is conducted at room temperature until the skinshave become sufficiently decolorized. These light colored skins are thenrinsed and can, if desired, be dyed in accordance with any of the wellknown or desirable processes employed for dyeing furs or the like.

It may be here stated especially in connection with the foregoingspecific example of applying the method of the present invention, thatthe preliminary killing operation may be omitted or combined with theimpregnating treatment. It may also be stated that salts or otherchemical compounds of a character compatible with the oxygen carrier maybe added to that solution prior to the treatment with the bleaching oroxidizing agent.

Examples of cyclic oxidizing catalysts are acetone-bisulfite, borax,ethyl-alcohol, glucose, urea,

and formaldehyde. Such compounds under the mild conditions used and inthe presence of hydrogen peroxides temporarily form intermediatesubstances containing more oxygen which is obtained from the oxidizingbleaching solution. They give up their absorbed or combined oxygenslowly to the fur skin or equivalent and are found in their originalstate at the conclusion of the bleaching action, as distinguished fromthe ferrous sulfate or other metallic equivalents, of other methods ofbleaching, which become 0xidized permanently to a higher state ofoxidation. The catalysts of the present invention suffer no finaloxidation.

Furthermore the catalysts are colorless compounds which are soluble inwater and are capable of readily absorbing oxygen from aqueous solutionsat room temperature. In this process these compounds exert no chemicalor tendering action either on the leather or hair of the fur skin at anystage of the bleaching process and they leave it unimpaired as tooriginal strength of leather and lustre of the hair.

The skins remain submerged in the solution of cyclic oxidizing catalystfor several hours until the fibres and leather are thoroughlyimpregnated. The excess of catalysts solution is then removed bysuitable means and the fur skins are then immersed in an oxidizingbleaching solution. The bleach may consist of hydrogen peroxide,perborates, or persulfates of any suitable strength, the quantity offree oxygen present being regulated by governing the hydrogen ionconcentration of the solution. The oxygen that is liberated from thebleach is immediately taken up by the catalyst which is contained in andadheres to the fur skin. The bleaching effect starts promptly and itsrate is controlled by the chemical liberation of oxygen from theoxidizing solution. In this way, I convert skins which were originallydark colored into skins possessing a light flesh color, being unimpairedas to structural strength, lustre and texture.

In my illustrative example the borax functions as an oxygen carrier, 1.e. cyclic oxidizing catalyst, becoming temporarily oxidized to sodiumperborate as an intermediate product. The intermediate compound beingunstable in aqueous solutions gives up its added oxygen in a gradualmanner to the fur skins that are being bleached. When acetone or itsaddition compounds are used as cyclic oxidizing catalysts, acetoneperoxides are formed as unstable intermediate compounds; and when ethylalcohol is used as the catalyst, ethyl-hydrogen peroxide or diethylperoxide are formed as the unstable oxidizing agents.

In prior practice, when metallic salts, a ferrous salt for example, isused as an impregnating agent, the metal salt takes up the oxygen withdrastic avidity until it becomes oxidized to a ferric compound. Then itno longer possess the power to take up oxygen; further bleaching of thefur skins depends then on the direct action of the bleaching oroxidizing agent on the hair of the skin.

The bleached fur skins obtained as a result of the illustrative exampleconsequently differ from fur skins which are treated with metal saltssuch as ferrous sulfate. In my process the catalysts and the bleachingagents and the products of reaction are all completely soluble inaqueous solutions. The bleached fur skins obtained after washing,therefore, resemble a natural light col ored fur skin in appearance andstrength and lustre of hair. When ferrous salts or its equivalents areused in conjunction with an alkaline peroxide of hydrogen solution inthe bleaching process, there is deposited into and onto the hair andleather of the fur skin a gelatinous precipitate of ferric hydroxide orequivalent metal hydroxide. Such precipitates are insoluble in water andgive the fur skins a characteristic coloration depending on the metalsalt that has been used. This precipitate furthermore causes a swellingon the inside of the hair and leather fibres thus weakening themstructurally.

The advantages and superiorities of my process are numerous and of greatpractical importance, and may be summarized as follows: The processmakes possible the bleaching of dark colored fur skins to a light orflesh color possessing the strength of leather and lustre of hair of theoriginal skin, and also enables the obtaining of such bleached skinsfree from metal discoloration and free of the injurious tenderingactivities induced by the presence of metal salts particularly those ina higher state of oxidation. Furthermore, my process permits aneconomical utilization of the bleaching and oxidizing agent because thecatalyst acts as an accumulator for the available oxygen and graduallyreleases it as the decolorizing process progresses. By my process theoxidizing or decolorizing activity is so controlled by the cyclicoxidizing catalyst that the accumulated oxygen is very graduallydelivered to the hair of the fur skin, thus avoiding the tendering andinjurious action which characterizes the use of metallic reducingagents.

What is claimed is:

1. The herein described method of bleaching animal fur skins, whichcomprises impregnating fur skins with a colorless soluble cyclicoxidizing catalyst, and subjecting the impregnated fur skins to anoxidizing bleaching action.

2. The herein described method of bleaching animal fur skins, whichcomprises impregnating fur skins with a colorless water soluble cyclicoxidizing catalyst, and subjecting the impregnated fur skins to anoxidizing bleaching action.

3. The herein described method of bleaching animal fur skins, whichcomprises impregnating fur skins with a cyclic oxidizing catalyst, andsubjecting the impregnated fur skins to an oxidizing bleaching action.

4. The herein described method of bleaching animal fur skins, whichcomprises impregnating fur skins with a colorless water soluble cyclicoxidizing catalyst, and subjecting the impregnated skins to an oxidizingbleaching and decolorizing action without the formation of insolublereaction products.

5. The herein described method of bleaching animal fur skins, whichcomprises impregnating the furs with cyclic oxidizing catalyst, and thenimmersing the impregnated furs in an oxidizing bleaching solution andpermitting the oxygen of the bleaching solution to combine with or beabsorbed by the catalyst and then given off slowly from the catalyst tothe fur skins.

6. The herein described method of bleaching fur skins, which comprisesimpregnating the furs with a water soluble cyclic oxidizing catalyst,and then immersing the impregnated fur skins in an oxidizing bleachingsolution and permitting the oxygen of the bleaching solution to combinewith or be absorbed by the catalyst and then given off slowly from thecatalyst to the fur skins.

'7. The herein described method of bleaching fur skins, which comprisesimmersing fur skins in a solution of a cyclic oxidizing catalyst untilthe TREATMENT & CHEMICAL MODE HEHG & DYEING; FLUiU CANON OF TEXTILES &FiBERS,

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solution of water soluble cyclic oxidizing catalyst until the hair andthe leather are impregnated with the catalyst, removing the excesscatalyst solution from the fur skins, and then immersing the impregnatedfur skins in an aqueous oxidizing bleaching solution containing freeoxygen and permitting the oxygen of the solution to combine with or beabsorbed by the catalyst and then given ofl slowly from the catalyst tothe fur skins.

WILLIAM E. POPKIN.

